The absolute threshold of a modality is examined by allowing the subject, in a series of trials, to directly adjust the stimulus in order to find the weakest stimuli detectable by them. The threshold is determined as the value that was detected 50% of the time.

A differential threshold is similarly explored allowing the subject, in a series of trials, to directly adjust the stimulus relative to a comparison stimulus until they can detect a difference. The threshold is determined to be the point at which the subject notes a just noticeable difference from the comparison stimulus on 50% of the trials